I love my four foot vivs for my corns, but the new ones we build are going to be three foot. So i think im quite lucky that i can fit in all the vivs i do need for the corns and royals, plus some spares for when i want to keep back hatchlings.
Im also having a pair of 6 foot vivs in the room too, for some future purchases.
I wouldnt personally keep my adults (corns) in racks, but thats because, i dont have enough time to get everyone of them out every week for a nice stretch and some exercise.
If i had big enough racks, i would keep my royals in them though, as they dont like to come out of their hides lol